shamshir, Thank you for posting in the Intel® Communities Support.
"my new laptop LAPQC71B supports ram 2666mhz . Does the motherboard support an upgrade of ram 3200mhz?", The answer is no, it is recommended, as per specifications, not to use a RAM higher different from DDR4-2666 since that is the max speed supported by the processor and the memory controller is located in the processor itself:
https://ark.intel.com/content/www/us/en/ark/products/196640/intel-nuc-9-extreme-laptop-kit-lapqc71b....
"This laptop has an RTX2070 max Q, but GPUZ shows me that the model is 10DE1F10 and not the maxQ 10DE1F50. Why?", Yes, the laptop works with"GeForce* RTX 2070 Max-Q" as you can see in the link above as well. Since this is a 3rd party tool, you will need to check directly with the manufacturer of GPUZ to confirm why it is not showing as Max-Q, even though in the picture you provided it shows it is the "GeForce* RTX 2070 Max-Q".
" can I change the temperature limit by uploading an other bios, because my card is limited in power at the temperature of 75°C", No, it cannot be changed by uploading another BIOS, the BIOS version for this laptop are available in sour Intel® website:
https://downloadcenter.intel.com/product/196640/Intel-NUC-9-Extreme-Laptop-Kit-LAPQC71B
The laptop works with the Intel® Core™ i7-9750H, the T-Junction of that unit is 100°C, so any temperature registry below that value is considered normal and expected:
https://ark.intel.com/content/www/us/en/ark/products/191045/intel-core-i7-9750h-processor-12m-cache-...
"And how can you explain that in performance mode my graphic card consumes 60w for delivering better performance than in normal mode with 80w. I don't understand that with less power, the card deliver more FPS.", That is exactly what the "performance mode" does, to be able to provide a high performance without that much power consumption and a balanced administration of the resources of the computer.
Any questions, please let me know.
Regards,
Albert R.
Intel Customer Support Technician
